I'm trying to connect a Windows PC to an embedded system via an RS232 link implementing SLIP. Ultimately I'll have a web server running on the embedded system. It seems that the only way to do this at the Windows end is to configure a dial-up with SLIP selected and pointing to an imaginary modem on COM1/2. At the embedded end I need to mimic the behaviour of a modem until the connection is set-up. I thought that all this would entail would be to send 'OK' after receipt of each AT command. However this isn't the case. I can get the Windows dial-up as far as Dialling but then it times out, presumably waiting for some response.
Does anyone know what the expected sequence of commands and responses is in this case please?
Well, the "modem" should at least return "CONNECT" when windows sends "ADTxxxx". All other AT commands from windows can be responded to by "OK" Try to dig up a Hayes command set description.
In Windows Dial-up networking select "Direct connection between two computers (COM1)". Then select baudrate, protocols, etc. When you dial out using that connection Windows will send out the string CLIENT, the embedded system would then reply with the string CLIENTSERVER. The CLIENT / CLIENTSERVER exchange takes the place of the usual modem stuff.
I don't think windows needs it per se, but his application (hyperterm?) may. IIRC, I couldn't get hyperterm to send data without it (even with hardware flow control disabled), but I may well be mistaken on that. I tend not to use hyperterm. ;-)
This is a comment from my 8051 slip code that appears right about where the problems begin. It might be helpful.
/* The COM port driver now believes that it has established a DTE to DTE link via 2 DCE (modem) devices. If DCD is not asserted by the device emulating the local DCE, then the port driver decides that the remote modem has hung up. It then shuts down the link and tries to hang-up the local DCE.
The local DTE will assert DTR whenever its ready to send data on a newly established link. We can link this to DCD to trick the COM port driver into thinking that the local DCE is receiving a carrier from the remote DCE, thereby signalling that the remote DCE has not hung-up and that all is well. This prevents the early SLIP link shut-down.
On a DB25 connector link pin 20 (DTR) to pin 8 (DCD), or for a DB9 connector link pin 4 (DTR) to pin 1 (DCD). */
Regards, Murray R. Van luyn.
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This is a comment from my 8051 slip code that appears right about where the problems begin.
/* The COM port driver now believes that it has established a DTE to DTE link via 2 DCE (modem) devices. If DCD is not asserted by the device emulating the local DCE, then the port driver decides that the remote modem has hung up. It then shuts down the link and tries to hang-up the local DCE.
The local DTE will assert DTR whenever its ready to send data on a newly established link. We can link this to DCD to trick the COM port driver into thinking that the local DCE is receiving a carrier from the remote DCE, thereby signalling that the remote DCE has not hung-up and that all is well. This prevents the early SLIP link shut-down.
On a DB25 connector link pin 20 (DTR) to pin 8 (DCD), or for a DB9 connector link pin 4 (DTR) to pin 1 (DCD). */
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